Burner with a perforated flame holder support structure

ABSTRACT

A furnace has a fuel and oxidant source to create a flow of combustible fuel and oxidant mixture, a perforated flame holder on which the flow impinges, and a support structure to support the perforated flame holder in a position where it at least partially contains combustion of the fuel and oxidant mixture. The support structure mechanically engages with the interior of the furnace to support the perforated flame holder, which may be movable within the furnace via a mechanism to optimize combustion or reduce NOx. The support may contain fluid coolant. The perforated flame holder may be moved into and out of a combustion region.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority benefit from U.S. Provisional Patent Application No. 62/117,943, entitled “BURNER WITH PERFORATED FLAME HOLDER SUPPORT STRUCTURE”, filed Feb. 18, 2015; and U.S. Provisional Patent Application No. 62/021,549, entitled “BURNER SYSTEM INCLUDING A MOVEABLE PERFORATED FLAME HOLDER”, filed Jul. 7, 2014; which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.

SUMMARY

According to an embodiment, a furnace includes a fuel and oxidant source configured to output fuel and oxidant, a perforated flame holder configured to hold a combustion reaction supported by the fuel and oxidant source, and a support structure configured to hold the perforated flame holder in alignment with the fuel and oxidant output by the fuel and oxidant source.

According to an embodiment, the support structure may further include a coolant space therein, the coolant space being bounded by a fluid-containment barrier, and the coolant space may be separated from combustion by the fluid-containment barrier.

According to an embodiment, heat may be removed from the perforated flame holder by putting the support structure into contact with a fluid coolant having a coolant temperature lower than a combustion temperature.

According to an embodiment, the support structure may include a mechanism configured to move the perforated flame holder relative to the furnace and/or the fuel and oxidant source.

According to an embodiment, the burner may further include an electronic controller with a processor and a sensor. The perforated flame holder may be configured to support a flame inside it when located at a distance from the fuel and oxidant source at which the fuel and oxidant flow has a predetermined range of velocities and a predetermined range of mix ratios. The electronic controller may be configured to operate a feedback loop that drives a perforated flame holder support mechanism to vary the distance between the fuel and oxidant source and the perforated flame holder. The electronic controller can thus cause the flame to be supported within the perforated flame holder.

According to an embodiment, an electronic feedback device including a processor running software embodied in a non-transitory medium can operate to drive a mechanism to move a perforated flame holder responsive to a detected condition such that a combustion reaction is held in the perforated flame holder. Holding the combustion reaction in the perforated flame holder can reduce undesirable combustion emissions.

According to an embodiment, a perforated flame holder can be supported by a mechanism configured to move at least a first portion of the perforated flame holder between a combustion region and a cooling region. Simultaneously at least another portion of the perforated flame holder can be moved from the cooling region to the combustion region so as to maintain heat output. While in the cooling region, the first perforated flame holder or portion of the perforated flame holder can be serviced and/or exchanged for a new perforated flame holder or portion thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partially cutaway view of a flame holder in a furnace, according to an embodiment.

FIG. 2 is a schematic view of a furnace having a movable flame holder, according to an embodiment.

FIG. 3 is a cross-section view of a furnace wall with a flame holder attachment configured to support a perforated flame holder support strut, according to an embodiment.

FIG. 4 is a cross-section view of a furnace wall with an alternative flame holder attachment configured to attach a perforated flame holder support, according to an embodiment.

FIG. 5 is an elevation view of a mechanism for engaging furnace tubes as part of a device to support a perforated flame holder, according to an embodiment.

FIG. 6 is an elevation view of a slider on a furnace tube acting as part of a support for a perforated flame holder, according to an embodiment.

FIG. 7 is an elevation view of a bracket acting as part of a support for a movable perforated flame holder support, the bracket holding a wheel that rides between two furnace pipes or tubes.

FIG. 8 is a cross-section view of a hollow support strut and bolt, according to an embodiment.

FIG. 9 is a partially cross-section view of a rail mounted to a furnace wall, in a furnace that lacks furnace tubes or pipes conveniently arranged to support a perforated flame holder, according to an embodiment.

FIG. 10 is a perspective view of a compound bolt configured to provide a removable attachment, to support a perforated flame holder, able to pass coolant through a furnace wall, according to an embodiment.

FIG. 11 is a cross-section view of flame holder tile with a hollow support framework holding segments of a perforated flame holder, the hollow support framework being capable of holding a cooling fluid, according to an embodiment.

FIG. 12 is a plan view of the embodiment of FIG. 11, according to an embodiment.

FIG. 13 is a cross-section view of a variation on FIG. 11, in which additional cooling features are added, according to an embodiment.

FIG. 14 is a perspective view of a cooling device to support a perforated flame holder on its upper surface, according to an embodiment.

FIG. 15 is a cross-section detail view of an integrated combination of the support and perforated flame holder according to FIG. 14, according to an embodiment.

FIG. 16 is a perspective view of a rotating perforated flame holder, according to an embodiment.

FIG. 17 is a perspective view of another rotating flame holder that includes hinged segments, according to an embodiment.

FIG. 18 is a perspective view of a perforated flame holder supported on a burner tile and having an adjustable elevation, according to an embodiment.

FIG. 19 is a schematic view of a first embodiment of a perforated flame holder support with a remote radiator, according to an embodiment.

FIG. 20 is a schematic view of a second embodiment of a perforated flame holder support with a remote radiator, according to an embodiment.

FIG. 21 is a schematic view of an example of a fire tube boiler with a perforated flame holder, according to an embodiment.

FIG. 22 is a perspective detail view of a perforated flame holder as also shown in FIG. 21, with the detail view illustrating perforations, according to an embodiment.

FIG. 23 is a cross-section view of a perforated flame holder support installed in the boiler of FIG. 21, according to an embodiment.

FIG. 24 is a partial cross-section view of a compression-force support that can support the weight of the perforated flame holder support illustrated in FIG. 23, according to an embodiment.

FIG. 25 is a plan view of a compression-force roller support with counterweight that can support the weight of the perforated flame holder support illustrated in FIG. 23, according to an embodiment.

FIG. 26 is a perspective view of a flame holder support with flame holder position adjustment, according to an embodiment.

FIG. 27 is a detail cross-section detail view according to FIG. 26, illustrating the mechanism for rotating the central rod, according to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

FIG. 1 is an illustrative diagram of a furnace 1100 including a perforated flame holder 1300, according to an embodiment. The furnace 1100 includes a wall 1103 defining an interior surface 1101 that defines an interior space 1106 of the furnace 1100 in which combustion takes place. The interior surface 1101 includes the inner surfaces of cylindrical and end wall portions of the furnace wall 1103. An exhaust vent 1102, fuel and oxidant source attachment plate 1203, and viewing windows (“sight ports”) 1104 and 1105 further define the interior space 1106 of the furnace 1100. The furnace 1100 may also include tubes, fittings, and the like not shown in FIG. 1. The furnace may have any suitable interior shape, such as for example a rectangular or circular cross section.

The furnace 1100 supports combustion to produce heat, which may be used for any suitable purpose. Furnaces are used for a wide range of industrial, commercial, and domestic applications such as steam generation for heating, propulsion, and generation of electricity; process heating used in oil refineries and other chemical plants such as for heating endothermic reactions, cracking petroleum, and heating distillation columns; metallurgical refining and production heating; kiln firing; and residential air and water heating systems. Other uses of furnaces will be apparent to those skilled in the art.

A fuel and oxidant source 1200 provides a flow of fuel and oxidant 1202 toward the perforated flame holder 1300, which is disposed transverse to the fuel and oxidant flow 1202. Although the fuel and oxidant flow 1202 is depicted, in FIG. 1, as being horizontal, the fuel and oxidant flow direction may be alternatively be upward, downward, or any angle therebetween. The fuel may be in the form of vaporized liquid, gas, or powdered solid, for example. The fuel and oxidant source 1200 can include one or more fuel nozzles (not shown) and one or more adjacent combustion air sources (not shown) arranged to cause the fuel to entrain the oxidant as the flow proceeds toward the perforated flame holder 1300. Alternatively, the fuel and oxidant source 1200 can include a pre-mix chamber or partial pre-mix chamber configured to introduce a premixed or partially premixed fuel and oxidant flow 1202.

The fuel and oxidant mixture 1202 has an overall (e.g., mean-average) velocity in a direction (leftward in FIG. 1), but alternatively may be considered in more detail as having a velocity described by a vector field. The overall velocity may then be characterized by the vector sum of the local vectors across a surface substantially perpendicular to the overall velocity, which may be but is not always generally parallel to an axis or plane surface of the furnace interior 1106. In an embodiment, the fuel and oxidant mixture 1202 may be created by a jet of fuel from a high-pressure orifice (fuel nozzle), which entrains air as it proceeds from the orifice and results in a jet that may have the general shape of a cone with an included angle of about 15 degrees.

In another embodiment, fuel and oxidant are introduced to a pre-mixing chamber, from which they pass, through a flame arrestor, into the interior space 1106 where combustion of the mixture 1202 takes place. In an embodiment, a flame arrestor (not shown) may include a body having parallel passages, openings, or tubes aligned generally with the direction of the overall velocity. In the flame arrestor, these are configured by a surface-to-volume ratio of the arrestor (and/or the surface-to-volume ratio of the parallel passages, openings, or tubes), by the thermal conductivity of the material from which the arrestor is made (e.g., metal), and by the length of the flow of the mixture 1202 through the arrestor, to exclude a flame from passing through the arrestor at a speed greater than or equal to the velocity, when the mixture 1202 has a predetermined mix ratio and the fuel has a predetermined heat value. Thus, flames are prevented from moving “backward” from the furnace interior space into the mixing chamber. The flame arrester can prevent a dangerous “flashback” condition, which can have an explosive result.

Inside the interior space 1106 of the furnace 1100, the applicants dispose a perforated flame holder 1300. In an embodiment, the perforated flame holder 1300 is configured to hold a flame and maintain stable combustion. In an embodiment, the flame holder 1300 may be configured by a surface-to-volume ratio thereof, by a thermal conductivity thereof, by a geometry thereof, and by a fluid flow length therethrough to contain a flame therein. Other factors such (as predetermined) fuel and oxidant flow velocity, fuel and oxidant mixture ratio, and fuel type, for example, can affect the ability of the perforated flame holder 1300 to hold and maintain stable combustion.

The perforated flame holder 1300 includes a plurality of through passages, and/or it may be porous. Perforated flame holders are described and discussed in the Applicant's Aug. 21, 2014 Publication WO2014/127311 A1, entitled “FUEL COMBUSTION SYSTEM WITH A PERFORATED REACTION HOLDER”, the contents of which, to the extent not inconsistent with the disclosure herein, are incorporated herein by reference. This publication alternatively refers to a “perforated reaction holder” as well as a “perforated flame holder”. In this application, “perforated reaction holder”, “perforated flame holder”, and “flame holder” are equivalent. The perforated flame holder of this application may be of any material, may be an electrical insulator or conductor, and may otherwise be varied. The perforated flame holder 1300 of this application may be used in any sort of external combustion heating device, for example a boiler or process furnace, herein generically referred to as a “furnace”.

Perforated flame holder 1300 may include or constitute a single integral piece that is extruded, drilled, or otherwise formed to define a plurality of perforations 1302; or, it may be discontinuous, formed from a plurality of pieces of material; or, it may be composite, for example, woven or sintered. The flame holder 1300 may include any suitable material; for example, it may include metal, ceramic, cementatious, or other refractory material. It may take any shape or form that provides (an appropriate) flow resistance, thermal mass, thermal conductivity, surface area, and etc., suitable for holding a flame inside, under given conditions of fuel heat value, mixture ratio, and flow rate through the flame holder 1300 (which is a function of the mixture velocity and other factors), or other variables. The perforated flame holder 1300 may include sheets, flakes or fibers.

The thermal, physical, and other characteristics of a flame holder, that relate to its ability to maintain a flame substantially within it under given ambient conditions such as fuel, mixture speed, mix ratio, and so on, are referred to herein as the “reaction parameters” of the flame holder.

The “perforated” embodiment of the flame holder 1300, that may include numerous through-passages, can be formed by drilling or otherwise forming holes through a solid block, by bundling lengths of tubing together, etc. FIG. 1 exemplifies these with perforations 1302, which are, for ease of illustration, depicted over only a portion of an “envelope” surface 1310 (the envelope surface might be exemplified by the shape of shrink-wrap over the perforated flame holder 1300, or by the shape of a flexible vacuum bag evacuated with the perforated flame holder 1300 inside). The flame holder 1300 is not restricted to any overall shape, but may include two surfaces over which the mixture 1202 enters and leaves the flame holder 1300, respectively, when in use.

Again considering FIG. 1, the perforated flame holder 1300 has an illustrative disk-like shape and perforations 1302, which pass through from a first or input flame holder surface 1310 to a second or output flame holder surface 1320, both of which exemplify envelope surfaces. The fuel and oxidant mixture 1202 from the fuel and oxidant source 1200 enters the input surface 1310 and may substantially burn inside, while combustion products leave the flame holder 1300 by the output surface 1320.

The flame holder 1300 is disposed or held in position inside the interior space 1106 at such a position (or positions) that, in view of the fuel flow rate, mixture velocity, and other variables, flame may be contained substantially between its envelope surfaces 1310 and 1320. To hold it in such a position, a support structure 1400 is provided to support the flame holder 1300 in at least one stable position at which the flame holder 1300 receives the fuel and oxidant mixture 1202 on the input flame holder surface 1310 and discharges the flow from a output flame holder surface 1320.

The support structure 1400 engages with the flame holder 1300 and also operatively couples to the furnace 1100. According to embodiments, the support structure 1400 is operatively coupled to the interior surface 1101 of the furnace 1100, to the fuel and oxidant source 1200, to the exhaust vent 1102, and/or to another structure (e.g. a steam tube) inside the furnace 1100. Various embodiments of the support structure 1400, described herein, provide hanging (tensile) support, compression member support, moveable support, and/or cooled support to the perforated flame holder 1300. In FIG. 1, the support structure 1400 is exemplified by a bolt 1410 passing into or through the wall 1103 of the furnace 1100, a strut 1420, a metal rim 1430, and two attachment points 1432. The hole where the bolt 1410 passes (not visible in FIG. 1) is an attachment point 1114 of the furnace 1100.

A viewing window or port 1104, 1105 may be disposed in the wall 1103, allowing the interior space 1106 and the flame holder 1300 to be imaged or otherwise detected by a sensor or sensors 1501 that may include cameras for flame imaging by visible light or other light, or sensors for detecting particular wavelengths of electromagnetic radiation (usually light, infrared, and ultraviolet). Other sensors 1501, such as sensors detecting the electrical conductivity of the gas in the interior space 1106, may be disposed exposed to the interior space 1106 of the furnace 1100. The sensors 1501 may provide information that is usable for feedback to adjust the furnace parameters to maintain flame or combustion inside the perforated flame holder 1300. Any suitable type of sensor may be included.

FIG. 2 is a schematic view of the feedback mechanism 1500, according to an embodiment. The sensors 1501 (shown in FIG. 1) can include one or more of an ultraviolet sensor (flame scanner) 1502, a video camera 1504, an infrared sensor 1506, and a gas conductivity sensor 1508, among others. These can be coupled to a processor or other electronic device 1510 that might also be coupled to the fuel and oxidant source 1200 and an actuator 1513. The infrared sensor 1506 can provide data about the temperature of surfaces, especially that of the input surface 1310 and output surface 1320 of the flame holder 1300. The ultraviolet sensor 1502 may indicate the presence of OH ions or radicals, which is an indicator of combustion. The still or video camera 1504 may image any flames and/or blackbody glow from the perforated flame holder 1300.

Data from the sensor(s) 1502, 1504, 1506, 1508 is used by the control processor or circuit 1510 to control the fuel and oxidant source 1200 to adjust the velocity and/or the fuel and oxidant ratio of the mixture, and the actuator 1513 can also or alternatively adjust the position of the fuel and oxidant source 1200 relative to the flame holder 1300, and/or move the flame holder 1300 relative to the furnace 1100 or the fuel and oxidant source 1200. With such a feedback mechanism, combustion can be optimized to maintain flame within the flame holder 1300, which can provide benefits for reducing oxides of nitrogen (NOx) and other pollutants.

FIG. 3, which is a partly cross-sectional view, according to an embodiment, illustrates one way in which a strut 1420, which can be part of the support 1400 (shown in FIG. 1), can be attached to the interior surface 1101 (shown in FIG. 1), at a point which is one example of an attachment point 1114, in this example, by a stud or bolt 1410. If the wall 1103 includes an outer steel shell and an inner lining of firebrick 1107, for example, as shown in FIG. 3, then studs or bolts 1410 are conventionally used to hold the firebrick 1107 in place, and are made long enough to do so. When the stud or bolt 1410 is made part of the support 1400, it may be extended into the interior space 1106 (shown in FIG. 1) a distance sufficient that another part of the support 1400, such as the illustrated strut 1420, is engageable with the interior surface 1101 by attaching to an end of the stud or bolt 1410. Thus, a conventional stud that is made longer than conventional (so that extra nuts can be used to attach something to the end) can be part of the applicants' attachment structure. The extra length, XL, may be considered as a non-conventional aspect of the applicants' stud. The bolt 1410 of FIG. 3 might also be used with continuous refractory, rather than firebrick.

FIG. 4, is also partly cross-sectional, according to an embodiment, which illustrates another type of stud 1410, which is fastened to the wall 1103 by a weld, and may be used with or without firebrick or refractory material 1107 as in FIG. 3, and may also be used on the inside of a pressure container, such as for example the inside of a fire tube in a boiler (a fire tube can be characterized as a furnace wall). Besides the threaded end illustrated in the drawing, the stud may be straight and may also end in a hook, loop, or other conventional structure used for attaching. This type of fixture is also applicable in the case of a furnace with refractory applied in a continuous layer over the inside surface of a steel shell.

Referring to FIGS. 1-3, the flame holder can be suspended via tension-bearing rods, cables, wires, chains, and so forth. One example of a tension-bearing member is the strut 1420, which may be in tension when located above the perforated flame holder 1300, the weight of which it is bearing (and in compression when located below); FIG. 6 (discussed below) shows a tension member 1476). Optionally, the perforated flame holder 1300 may be movable on these rods, cables, wires, chains, and so on. If such tension-bearing members run parallel to at least a portion of the velocity of the mixture 1202, then the flame holder 1300 is easily moved toward and away from the fuel and oxidant mixing fuel and oxidant source 1200 in a way to affect the action of the flame holder 1300, or, to preheat the flame holder via a conventional flame. For example, in a large, vertically-fired furnace a flame holder may be suspended on chains or cables (such as 1476 in FIG. 6) that run through furnace-wall openings, such as the exhaust vent 1102, to a windlass mechanism or the like (not shown). Heavy chains may be advantageous for such use because they would provide some positional stability. Pure tension members such as cables or chains might also support a flame holder, as a tension member, in the manner of a gondola supported on an aerial cable. A flame holder may be supported on one or several such tension members that run parallel to one another (similar to a suspension bridge), and may include a mechanism for moving the flame holder along their length. Chain, for example, may be engaged with a mechanism that engages the chain and works along from link to link (not shown). Also, relatively stiff rods or tubes (e.g., 1450 in FIG. 9, discussed below) can replace the flexible cable or chain, which may reduce the amount of tension needed to support the flame holder against its weight or against fluid forces. Rods and tubes may alternatively, or in conjunction, be used as rails rather than as suspension members.

A tubular shape more efficiently resists bending than does a rod of the same cross section and same tension resistance. Therefore a tube or pipe can be used as a rail, as well as being used as a purely tensioned suspending member, and can support a flame holder other than in a hanging position against gravity (or in tensile opposition to other tension members). A tensioned suspending member, such as a rod or tube, can be coiled to impart a lower spring constant, which may be advantageous in some situations, for example in a marine boiler that is subject to acceleration forces and in which some shock mounting may be advantageous. (A coiled tension member 1474 is shown as part of a suspended member in FIG. 6, discussed below.)

A flame holder may be suspended inside a furnace, in any orientation, by pure tension members that are suitably arranged and attached at respective points to the interior surface 1101, without any of the support members being loaded in compression or bending. In such an arrangement, tension members with a relatively low spring constant can provide for thermal expansion effects as well as shock-mounting. For example, a generally-planar flame holder might be suspended by one straight vertical tension member and two coiled tension members, where the three tension members made angles of approximately 120 degrees between them. (Three tension members 1413 are shown in FIG. 18, discussed below.) The one straight member would fully support the weight, leaving the other two to maintain the flame holder position relative to the furnace interior wall and absorb thermal expansion and contraction, as well as shocks.

In an embodiment, the perforated flame holder 1300 can be supported entirely by compression members. Also, a flame holder can be supported by a combination of tension and compression members. One example is where the weight of the flame holder is counteracted by a torque due to tensile and compressive members. For example, a flame holder may be supported by a truss acting as a cantilever beam. FIG. 23, discussed below, shows an example of this in support structure 602.

If a flame-holder-supporting member serves as a rail that is subjected to bending loads, then coiling may greatly reduce its bending stiffness, so a straight or curved rod or tube would be preferred. (An example of a rail is 1450 in FIG. 9, or 700 in FIG. 7, discussed below.) A rail, whether solid or hollow, may generally need a certain amount of stiffness to resist loads, such as the weight of the flame holder. The lateral spring constant of a rail depends on its length and whether the ends are fixed or jointed, as well as its material and transverse moment of inertia, as is known to those skilled in the art of strength of materials. According to an embodiment, the support structure 1400 includes a rail configured to make the position of the flame holder 1300 adjustable. For example, the strut 1420 of FIG. 3 may run along the interior surface 1101 of a furnace, such as the exemplary cylindrical surface shown in FIG. 1, extend to a second bolt or stud to which it attaches in a similar manner, and serve as a rail (like rail 1450 or 700, mentioned above). Two or more such rails, mutually parallel and spaced around the circumference of the interior surface 1101, may be sufficient to constitute a track on which a perforated flame holder slides or rolls, or, be clamped into a fixed but adjustable position. A single, wide rail may alternatively be used.

A flame holder can be mounted to a rail by screws, clamps, sliders, rollers, wheels, gears, etc. In some embodiments, it may be advantageous to be able to adjust or move the flame holder, especially in regard to its distance from the fuel and oxidant source 1200. Therefore, the applicants contemplate that a flame holder may be supported so as to allow for motion along the rail(s).

Optionally, one or more of the rails can be rotatable and threaded to intercept a female thread or nut fixedly coupled to the perforated flame holder 1300. Another possibility is to use a rack-and-pinion or worm-and-wheel arrangement, with teeth provided on the rail meshing with a worm or pinion gear coupled to the perforated flame holder 1300. Still another possibility is to let the support 1400 slide on the rail, but be located by a cable, rod, or other mechanism that is not involved in the contact of the perforated flame holder 1300 and the rail (see, e.g., FIG. 6).

The applicants also contemplate a support that is adapted to furnaces of the type having tubes (e.g., process heaters, water-tube boilers), which are part of the interior and include part of the interior surface 1101 of the furnace. Such furnaces may have tubes that are horizontal or vertical, although the tubes are sometimes inclined, as for example when the tube is helical and the tubes is at a shallow angle. The tubes, which are often separated from a refractory wall and each other by some distance, may be disposed in a vertical plane on either side of a row of burners on the floor of a furnace, or, may fire toward a single plane of tubes from either side; there are many configurations.

A perforated flame holder 1300 may be suspended from the tubes. A support may engage with tubes via conventional hardware such as hooks, pipe clamps, and the like, and these are contemplated by the applicants to be at least part of a support for a perforated flame holder 1300. However, it may be desirable to adjust the position of a perforated flame holder 1300, or to change it in response to changing conditions, for start-up, etc.

FIG. 5 illustrates a mechanism for adjustably supporting a perforated flame holder 1300 (see FIGS. 1, 2, 11-13, 17 and 18) on horizontal tubes 1160 adjacent a refractory wall 1107, according to an embodiment. (The tubes 1160 here exemplify an attachment point.) A large gear wheel 1460 meshes with the tubes 1160, just as a pinion meshes with a rack gear. The large gear wheel 1460 is unitary with an axle 1462 and a wheel gear 1464 that meshes with a worm gear 1466, which in turn is fixed to a drive shaft 1468. Turning the drive shaft 1468 may cause the large gear wheel 1460 to climb or descend the column of tubes 1160. In a furnace of the type having horizontal tubes adjacent two facing refractory walls, a horizontal perforated flame holder 1300 may be suspended on a plurality of large gear wheels 1460, and these gears may be driven by their respective drive shafts 1468 from a common driver, using linkages, chains, belts, gear trains, or individual motors as are known in the art. This can permit the horizontal perforated flame holder 1300 to be raised and lowered from a floor on which are disposed burner assemblies, even when the furnace volume is long in the direction of the tubes 1160.

An alternate apparatus (not illustrated) for suspending a perforated flame holder 1300 from horizontal tubes in a furnace might include a hinged track with a hook on each segment, with the hinged track being moved over rollers, as is a tank tread. The track segments could have a length such that the hooks engage the tubes sequentially. This arrangement would distribute the weight of the perforated flame holder 1300 over several tubes.

FIG. 6 shows a rolling support 1470 engaging a vertical tube 1160. The rolling support may have several rollers (or wheels) 1472 engaging the surface of the tube 1160, according to an embodiment. In the example of this figure, there are three wheels 1472, one of which is spring-loaded by a spring 1474 tending to clamp the tube 1160 between the wheels 1470. One or more of the illustrated rolling support 1470 may be attached to a perforated flame holder 1300 (see FIGS. 1, 2, 11-13, 17 and 18) in various ways to serve as a means for adjusting the vertical position of the perforated flame holder 1300. The rolling support 1470 may be modified with rough wheel surfaces for gripping, motors, gears, and so on. Also, the rolling support 1470 may be used in conjunction with a cable, rod, chain or other pure tension member 1476 that might control or adjust the vertical position of the perforated flame holder 1300, while the rolling support 1470 serves to locate the perforated flame holder 1300 within the horizontal plane and does not affect its height.

FIG. 7 shows a wheel 676 riding on two adjacent parallel water tubes, process tubes, or rails 700, with the wheel 676 being mounted on a bracket 675 that can be part of a movable perforated flame holder support, according to an embodiment. This embodiment is suited to non-cylindrical, prismatic combustion volumes, such as those having a generally square cross-section defined by parallel tubes, as well as to a cylindrical combustion volume. A furnace can become quite hot, and not only a rail, but also a strut or a tensioned or compressed suspending member, can be embodied as a hollow tube or pipe into which coolant may be introduced so as to keep the suspending member cool enough to avoid heat failure. A small amount of water injected into the tube or rail might keep its temperature safely below the softening point, even while the furnace is hot enough to soften the material from which it is made; or, air or some other coolant can be forced through via a pump. In view of this, there may be cases where the metal support of a perforated flame holder 1300 (see FIGS. 1, 2, 11-13, 17 and 18) (and optionally, thereby the perforated flame holder 1300 proper) might advantageously be cooled via fluid coolant and a fluid-guide structure (which could be a fluid-containment structure as well). Cooling fluid, whether steam or air or some other fluid, can be circulated through a support member and out, or, merely vented into the furnace. In the case of an updraft furnace, where blocks of ceramic are used in the perforated flame holder 1300, the blocks may rest on a metal frame, which may need little cooling other than that provided by un-combusted mixture; but in other situations, extra cooling may be desirable to avoid the use of expensive, very heat-resistant metals or to allow higher furnace temperatures.

For example, if the bolts or studs 1410 shown in FIG. 3 and FIG. 4 were bored, or fabricated from pipes or tubes, then water or some other coolant could be introduced into the furnace through them, and the coolant could be transferred to other members of the support, if they were also hollow. One embodiment of this is shown in FIG. 8, which is a cross-section of a bolt or stud 1410 with a central bore. The central bore makes hydraulic contact with a second bore in a strut 1420, via a conical press-fit as shown. These bores exemplify an interior space 1499. Nuts are not shown, but a lower nut might hold firebrick in place, while an upper nut might compress the strut 1420 onto the conical portion of the bolt or stud 1410 and thereby hold it in a position with friction, as well as sealing the hydraulic passage.

Also, the fastener and strut 1420 of FIG. 3 might be replaced by a unitary U-shaped rod or tube, so as to form a rail that can be welded to the furnace wall 1103, or bolted by exterior nuts after the legs are passed through two holes in the wall 1103. This is illustrated in FIG. 9, where a U-shaped tube (or rod) 1450 is welded to the steel wall 1103 (other fastening can be used), according to an embodiment. The tube 1450 protrudes over an exemplary continuous layer of refractory material 1108 held in place by anchors 1109. The tube 1450 could be welded to the interior surface, but in FIG. 9 it is shown passing through holes in the wall 1103, and having couplings 1451 for attaching to a source and drain of cooling fluid. Radiative heat transfer to the tube 1450 can be reduced by placing it near to the refractory material 1108.

As mentioned above, the perforated flame holder 1300 may, in an embodiment, be made with a ceramic element or elements and this ceramic may be held by a metal frame, as metal often is tougher than ceramic and has greater tensile strength and workability. For example, in exemplary FIG. 1, the perforated portion may include ceramic but the circumferential periphery may include a metal rim 1430. Being in contact with the perforated flame holder 1300, which is a source of great heat because combustion substantially takes place inside it under the applicants' conditions, the metal rim 1430 may reach a high temperature. If it is desired to keep the rim cool, for example to avoid heat failure, then it may, in an embodiment, be made hollow and cooled with internal fluid. To this end, cooling fluid may be conducted to the hollow rim 1430 via one or more hollow struts 1420 such as are shown in FIG. 8, and circulate through the rim 1430, then to be vented from a hole that may be midway between struts 1420, or else leave the furnace through another strut.

FIG. 1 depicts two struts 1420, but may be interpreted as failing to show two more struts 1420, due to the cut-away of the wall 1103 for purposes of illustration. In this figure, attachment points 1432 might be places where the two not-shown struts could be attached to the rim 1430, for example by bolts if the holes 1432 are female-threaded holes. The holes 1432 are merely exemplary of other fastenings, such as studs, welds, clips, etc. If the attachments 1432 are embodied as studs, for example, then the coolant-conducting structure shown in FIG. 8 might be used to conduct fluid into the rim 1430.

It will be understood that the struts need not be distinct from the perforated flame holder 1300, and a support for the perforated flame holder 1300 need not be more than an attachment (e.g., a fastener) between the furnace 1100 and the perforated flame holder 1300 proper. As just one example, one of the bolts illustrated in FIG. 8 might be inserted directly into the periphery of a perforated flame holder 1300, which would include a space to accept the bolt. Furthermore, as illustrated in FIG. 10, according to an embodiment, a hollow bolt 1440 having an axial bore exemplifying an interior coolant space 1499 (shown in cross-section view) could be used to hold the firebrick via a nut (not shown), and a thinner bolt 1442 (shown in plan view) could be inserted through the hollow bolt 1440 to attach a perforated flame holder 1300 via a threaded hole in its support (e.g., if the attachment 1432 of FIG. 1 were a threaded hole, then the thinner bolt 1442 could engage it). Moreover, the thinner or inner bolt 1442 might itself be bored as shown to conduct cooling fluid, and include a head coupling 1443 for fluid connection (coupling 1443 is exemplified by pipe thread in the FIG. 10).

In general, any of the hollow members mentioned above, such as the U-shaped tube 1450 of FIG. 9, can be used to conduct fluid for cooling portions of a flame holder support.

FIG. 11 shows a composite metal and ceramic perforated flame holder 1300 and support structure 1400 in cross section, while FIG. 12 shows the same perforated flame holder 1300 and support structure 1400 in plan view, according to embodiments. The embodiment of the support structure 1400 in FIG. 11 and FIG. 12 includes a metal grid 1452 that includes hollow members with an interior space 1499 that can conduct cooling fluid, and which are shaped to accept and hold sections of perforated ceramic 1354 (“cartridges” or “tiles”) that are included in the perforated flame holder 1300 in the illustrated embodiment. The plan view of FIG. 12 shows one possible configuration with square ceramic sections 1354 and a square outline to the perforated flame holder 1300. The square's corners 1201 are round, to indicate that fluid-supply pipes are entering the grid from below (hidden in this figure). In this view, the fuel and oxidant source is located beyond the perforated flame holder 1300. Vent holes 1455 are located so as to force cooling fluid to flow through all parts of the grid 1452.

FIG. 13 shows an alternate embodiment of the support structure 1400 of FIG. 11 and FIG. 12, which may use the cooling effect of un-burned mixture to keep parts of a flame holder support structure 1400 relatively cool. This figure shows that the cross-section of the grid 1453 (generally similar to the grid 1452 of FIG. 11 and FIG. 12) includes a descending portion 1457 of arbitrary length as indicated by horizontal break lines, and it also contains a mesh 1456 that may allow the grid 1453 to act as a heat pipe by conveying liquid 1459, via capillary action, upward to the combustion region inside refractory portion 1354 of the perforate flame holder 1300. The grid may contain a material 1459 such as sodium, which melts at only 208 degrees F. and boils at 1621.3 degrees F. (883 C); thus, in a furnace, sodium is expected to be either a liquid or a gas inside the grid 1453. (Sodium is used as a coolant inside the exhaust poppet valves of IC engines.) Liquid sodium may move up the mesh 1456 by capillary action and evaporate into a gas that may then condense in the descending portion 1457, transferring heat to the grid 1453 and to the incoming mixture; the heat of vaporization of sodium is comparable to that of water, so heat transfer may be efficient.

Materials 1459 other than sodium can be used as a working fluid in the applicants' heat-pipe embodiment. Zinc, for example, boils at 907 C (1665 F) and is less reactive than sodium; it is about as reactive as iron, although it may burn in air, unlike iron. Its melting point is, however, higher at about 420 C (787 F). Other materials, such as thallium and calcium, might also be used. In this embodiment the hollow grid 1453 could be evacuated rather than filled with air, to enhance the heat-pipe effect. A pressure-relief valve in a vent tube leading to a remote container can be provided, to prevent explosion in case of overheating.

The heat-pipe principle could also be used in an all-metal perforated flame holder having the general configuration of a hollow volume perforated by fire tubes, as in a fire-tube boiler that contained sodium, zinc, etc. rather than water and steam. Such an embodiment of a perforated device is shown in FIG. 14 and FIG. 15. Here, the metal grid 1452 includes a sealed can with metal tubes 1458 running from one surface to the other, and with joints between the cylindrical sides, upper and lower surfaces, and tubes sealed hermetically (for example by welding). The inside is evacuated, except for an amount of volatile metal 1459, and the interior surfaces are at least partly covered with capillary mesh 1456.

This device would tend to create a region of uniform temperature between a hot side and a cool side, and could be used alone or in combination with other devices in a perforated flame holder as both a thermal zone regulator and a rigid mechanical support structure for any perforated flame holder 1300 (see FIGS. 1, 2, 11-13, 17 and 18) parts or layers (since the grid 1452 would include a strong and rigid “stressed-skin” structure). An exemplary ceramic layer 1355, with perforations aligned with the tubes 1458 to allow gas passage, is shown exploded away from the grid 1452 in FIG. 14.

FIG. 15 shows another embodiment, with ceramic inserts 1359 inserted into the tubular perforations 1458 of such a device, which could provide a desired temperature environment and/or a desired temperature gradient for combustion, and could bring temperatures inside the tube 1458 to a desired temperature, for example, 2500 F (1400 C), due to the insulating effect of the ceramic inserts 1359 between the grid 1452 and gases undergoing combustion. Similarly to the perforated flame holder support structure 1400 of FIG. 13, that of FIG. 15 may contain a volatile metal 1459. The devices of FIG. 11 and FIG. 15 may be considered as topological equivalents in some embodiments.

In a non-illustrated variation, the grid 1452 of FIG. 14 may be covered over all or most surfaces with a layer of ceramic, either by a surface coating or by discrete surface-covering parts, or otherwise. Such a device could tolerate high surface temperatures but would minimize the heat outflow needed to keep the metal grid 1452 from melting; the heat flow from the flame reaction to the support would be reduced by the insulating effect of the ceramic coating. An external radiator could be provided, if needed, to condense the metal vapor. Such a device might be used in a jet engine, for example, as well as in a furnace.

Regardless of its cooling features, the perforated flame holder 1300 embodiments of FIG. 11, FIG. 12, and FIG. 13 may constitute an example of the applicants' “cartridge-loaded” perforated flame holder 1300. In relation to these figures, one perforated flame holder element 1354 contemplated by the applicants is a commercially-available perforated ceramic tile (also called a “monolith”) measuring 2 by 6 by 6 inches, with the perforations running between the two 6-by-6 inch square surfaces (here, the “envelope” surfaces). Other sizes, up to 14 by 16 inches, are available. The illustrated grid 1452, if oriented as shown, will hold the tiles 1354 by gravity but may allow the tiles to be readily lifted up and out, and then replaced. This may allow replacement of tiles during furnace operation, by reaching through an inspection window such as 1104, 1105, or some other opening, with an elongated tool. To hold the tiles in place regardless of gravity, the grid 1452 might include rotatable fingers or crosses at the grid intersections and corners, which can be made of high-temperature metal or ceramic (not shown).

The descending portion 1457 of the grid 1453 in FIG. 13 illustrates another aspect of the applicants' cooling, that relates to the position of the support 1400. A heat-sensitive part, such as a strut, may in general be cooler if it is on the fuel and oxidant source side of the perforated flame holder 1300, rather than on the other side. This is because combustion may take place, ideally or as intended, inside the perforated flame holder 1300, and in general the flow of fluid (mixture, air, combustion products) is hotter downstream of the perforated flame holder 1300. Therefore, one aspect of keeping a flame-holder support cool is locating it in an upstream direction rather than downstream.

Another example of this principle is in FIG. 1, where it is seen that the struts 1420 are canted in the upstream direction, rather than being rotated a half-turn to cant in the downstream direction. With the illustrated cant, the struts 1420 tend to be immersed in cooler fluid, which counteracts the temperature effect of conductive or radiative heat from the perforated flame holder 1300. The same idea may apply to other parts that are involved in moving the perforated flame holder 1300. The truss mentioned above, for example, might be fastened to the interior surface 1101 adjacent to the fuel and oxidant source 1200, but support a perforated flame holder 1300 in a downstream location.

FIG. 16 illustrates a truncated-conical embodiment 1322 of a perforated flame holder (that, in an embodiment, can include a metal rim 1423 as a perforated flame holder support structure) that rotates on driven and/or idler rollers 1424 (the drive mechanism is not shown). Here, rotation of the perforated flame holder 1322 around its geometrical axis continually brings new areas of the perforated flame holder 1322 into the combustion region above the fuel and oxidant source 1200, and then removes those areas before they become over-heated, placing them into a cooling region away from the combustion. The temperature differential between the cooled portion of the perforated flame holder 1322 entering the combustion region, and the heated portion leaving the combustion region, can be controlled by adjusting the rotation speed of the perforated flame holder 1322. Optionally, an average temperature of the perforated flame holder 1322 can be controlled by adjusting the average temperature of the perforated flame holder's 1322 environment. For example, if extra cooling is needed to bring the average flame-holder temperature down, then air can be forced through the perforated flame holder 1322 in the cooling region by means of shrouds adjacent to the inner and outer opposing surfaces of the perforated flame holder (not shown), or the perforated flame holder 1322 can be sprayed with water, etc. If air is used as a coolant, then part of the air feed to the fuel and oxidant source 1200 can be diverted through the perforated flame holder 1322. Thus, in the combustion region above the fuel and oxidant source 1200 the average temperature and also the temperature gradient can be controlled.

The rollers 1424 may grip the perforated flame holder 1322 at its outer edge as shown. If the outer edge is unable to separate from the rollers (as a roller-coaster car is unable to separate from its track), then the perforated flame holder 1322 can be cantilevered and the rollers 1424 may be kept away from the combustion area, regardless of the orientation of the furnace and fuel and oxidant source 1200. Three rollers 1424 may suffice to fix the axial orientation and position of the perforated flame holder 1322.

Among the variations on the embodiment of FIG. 16 contemplated by the applicants are rotating discs, rotating cylinders, and flexible linkages resembling tank treads, wherein each of the links contains one or more perforated flame holder 1322, and the linkage is moved perpendicular to the axes of its link hinges. FIG. 17 shows a chain of segments of a perforated flame holder 1300 are linked by hinges 1422, that constitute part of the perforated flame holder support structure 1400 in this embodiment.

Embodiments of a perforated flame holder 1300 that is movable relative to a fuel and oxidant source 1200, transversely to the mixture flow direction, are described above in relation to cooling of the perforated flame holder 1300 and its support structure 1400, herein. Elsewhere, relative motion of a perforated flame holder 1300 and a fuel and oxidant source 1200, in a direction that is substantially parallel to the mixture 1202, have been described in relation to maintaining combustion substantially inside the perforated flame holder 1300. However, relative motion in the flow velocity direction may also be involved with raising and lowering the perforated flame holder 1300 temperature, especially with raising the temperature at the start of combustion. This is because the perforated flame holder 1300 may need to be pre-heated by a conventional flame (in which combustion occurs between the fuel and oxidant source 1200 and the input surface (not shown) of the perforated flame holder 1300); then, after the flame heater reaches the appropriate temperature, the distance and/or reaction parameters may be adjusted to keep the flame inside the perforated flame holder 1300.

FIG. 18 shows a burner tile 1112. Burner tiles are commonly used as part of a furnace burner, and a fuel and oxidant source for mixing fuel and oxidant is often near or inside a burner tile. The burner tile 1112 may be that part of the furnace interior which is closest to the fuel and oxidant source, and it also may be the part of the furnace interior which is most precisely located relative to a fuel and oxidant source. Furthermore, the space within the burner tile may contain the points closest to the fuel and oxidant source, while the space in front of the burner tile is may be free of obstructions. For these reasons, the applicants contemplate that a burner tile may interact or mechanically couple with a flame holder support structure 1400.

In FIG. 18 a perforated flame holder 1300 is held on a support 1400 that is in contact with a conventional burner tile 1112, according to an embodiment, which in FIG. 18 has the cylindrical symmetry found in some burner tiles (another common type is rectangular). The rim 1430 of the conventional burner tile 1112 is an area that the support structure 1400 can couple to, and the support structure 1400 includes generally C-shaped grapples 1412 to engage the rim 1430 and thereby locate the support structure 1400. The support structure 1400 may grip the rim 1430 or it may be forced onto the rim 1430 by tension or compression members such as springs or struts 1413 (two of three are visible in the figure, the other is obscured). The exemplary support 1400 also includes risers 1415 that are aligned generally with the velocity of the mixture coming from the fuel and oxidant source 1200 inside the burner tile 1112 (not visible in FIG. 18), on which the perforated flame holder 1300 is movable toward and away from the burner tile 1112 on sliders 1416, which, as shown, may include electric motors coupled to gears or wheels engaging the illustrated serrations or rack-gear teeth along the side of each riser 1415. Other known mechanisms for adjusting the position of the perforated flame holder 1300 may also be used, or, the perforated flame holder 1300 may be removably clamped, welded, or otherwise permanently or adjustably fixed in a position by conventional means.

In the illustrated device the perforated flame holder 1300 has a diameter that may not allow entry into the concave part of the burner tile 1112, but the device may be designed such that the perforated flame holder 1300 can enter the conventional burner tile 1112. Mixing devices such as fuel jets are often inside a cylindrical burner tile, but may also be disposed around its periphery, and in that case the perforated flame holder 1300 might be larger.

Those skilled in the art can modify the support and perforated flame holder 1300 of FIG. 18 for a rectangular burner tile, for a row of burners, and so on, merely by changing the shape.

FIG. 19 shows an externally-cooled support system 1600 for a perforated flame holder support 1452, similar to that of FIG. 14, with through-tubes 1458, according to an embodiment. Although the illustrated device resembles that of FIG. 14, but the schematic drawing figure is not limited to any one embodiment and might also represent, e.g., rim 1430 of FIG. 1 or the grid 1452 of FIG. 11, for example. These examples all include internal hollows 1499 that may contain coolant, and in general the structure illustrated in FIG. 19 may be disposed inside any perforated flame holder support structure.

In some embodiments, the illustrated fluid-containment structure is closed and relies on surface cooling to remove heat from the coolant (as in the descending portions 1457 of FIG. 13). In other embodiments, the fluid-containment structure may also include a fluid connection between a coolant containment volume thereof and space outside of the perforated flame holder and also outside of the furnace. The fluid connection may in one embodiment include a tube 1620, as illustrated in FIG. 19. This tube 1620 may include a fitting 1621 that can be used for coolant filling, evacuation of air, etc. The tube 1620 may act not only as a coolant conduit but also as a support to support the perforated flame holder 1600 in a designated position. In one embodiment (not illustrated), the tube 1620 can include a hollow strut and/or an attachment to an interior of a furnace, and may conduct the coolant through a wall of a furnace 1100. (e.g., FIG. 8).

The tube 1620 may optionally pass through the wall of a furnace 1100, also indicated schematically by a dashed line, and reach a heat radiator 1622 located in the space outside of the perforated flame holder 1600 and also outside of the furnace 1100. In this way the heat radiator 1622 is fluid-coupled to the coolant containment volume inside the perforated flame holder 1600 by the connection tube 1620.

FIG. 20 schematically illustrates optional additions to the cooling support system of FIG. 19 that include a fan 1623, a coolant reservoir 1624, a pump 1625, a pump control 1626, and a temperature or flame sensor 1627 which may be located inside the furnace 1100 or may image the perforated flame holder through a window (neither illustrated in FIG. 20), according to an embodiment. The pump control 1626 may operate the pump to control or limit the temperature of the perforated flame holder 1300.

FIG. 21 shows an example furnace, embodied in a low NOx fire tube boiler 200 including a flame holder that is here, according to an embodiment, exemplified as a perforated flame holder 202. A combustion pipe 106 can also be referred to as a fire tube, and may be horizontal as shown in the illustrated example, or vertical, or tilted. In the exemplary fire tube boiler 200, it also holds water 104 out of the combustion volume 108. The combustion pipe 106 is characterized by a length and an inside diameter, and surrounds the combustion volume 108 which communicates with an exhaust vent 128. The fire tube boiler 200 includes a shell 102 having an exterior wall 103, a back wall 105, and a peripheral wall 107 configured to hold water 104.

A fuel nozzle 110 is disposed to receive fuel from a fuel source 112, coupled to a valve 138, and output a fuel jet 206 into the combustion volume 108, and also an oxidant source 114 is disposed to output combustion air into the combustion volume 108. The oxidant source 114 can consist essentially of a natural draft air source, or alternatively can receive oxidant from a blower 116. Various fuels are used in commercially available fire tube boilers. In other embodiments, the fuel might be solid, or a mix of solid, liquid, and/or gas, alone or in combination. Hot flue gas that is circulated through exemplary “fire” tubes 120, 122 that, together with the wall of the combustion pipe 106 transfer heat produced by the combustion reaction 118 to the water 104. In the illustrative example, the fire tubes including the combustion pipe 106, 120, 122 form a three pass system with hot flue gas being produced in the combustion pipe 106 flowing from left to right, a second pass of fire tube 120 supporting flue gas flow from right to left, and a third pass of fire tubes 122 supporting flue gas flow from left right. Each “turn” of flue gas direction is made in a plenum 124, 126. FIG. 22 is a view 400 of an exemplary perforated flame holder, which, in the illustrated example, includes the perforated flame holder 202 of FIG. 21, according to an embodiment. The perforated flame holder 202 includes a body 210 that defines a plurality of void volumes 212 operable to receive and convey fuel and oxidant, to hold a combustion reaction supported by the fuel and oxidant, and to convey and output combustion reaction products. The body 210 defines an input surface 302 configured to receive the fuel and oxidant, an output surface 304 opposite to the input surface 302, and a peripheral surface 306 defining a lateral extent of the perforated flame holder 202. In some embodiments, the void volumes 212 include a plurality of elongated apertures 308 extending from the input surface 302 to the output surface 304 through the perforated flame holder 202. In some embodiments, the elongated apertures 308 can each have a lateral dimension D.

In other embodiments not shown, the perforated flame holder 202 might have a different shape and/or extra parts, and may include or function as an electrode whereby electrical voltages or currents, magnetic or electric fields, flame sensors and signals therefrom, and the like may influence the flame. Such non-illustrated parts may be coupled to a processor and electrical apparatus, not shown.

The perforated flame holder 202 can be disposed substantially adjacent to the combustion pipe 106 around its entire body 210. Additionally or alternatively, the perforated flame holder 202 can be disposed at least partly separated from the combustion pipe 106 such that natural flue gas recirculation can occur.

FIG. 23 is a side sectional view 600 of a portion of a boiler including a support structure 602, for supporting the perforated flame holder 400 within a combustion pipe 106, according to an embodiment. The support structure 602 has several functions in support of the perforated flame holder 400, among which are physical support (e.g., holding position against gravity and/or fluid forces), deployment in a specific desired location or orientation, and alignment (geometric centering and/or rotation to an axially aligned orientation. The support structure 602 may also provide active features such as axial motion to a desired position, rotations, tilting, or the like, which may be actuated from outside the combustion device.

The fuel nozzle 110 can be characterized by a nozzle diameter through which fuel is emitted. The perforated flame holder support structure 602 is operatively coupled to the perforated flame holder 400 and configured to hold the perforated flame holder 400 at a dilution distance (D_(D)) from the fuel nozzle 110.

The shell 102 (see FIG. 21) can include an exterior wall 103 peripheral to the combustion pipe 106. A cover plate 604 can be included and operatively coupled to the exterior wall 103. The perforated flame holder support structure 602 can be operatively coupled to the cover plate 604. The cover plate 604, the support structure 602, and the perforated flame holder 400 can be configured to be installed in the combustion pipe 106 as a unit without a mechanical coupling to the combustion pipe 106.

The fuel nozzle 110 and the oxidant source 114 together can include an exemplary fuel assembly or fuel and oxidant source 606. The fuel assembly 606 can be operatively coupled to the cover plate 604. The cover plate 604, the fuel assembly 606, the support structure 602, and the perforated flame holder 400 can be configured to be installed relative to the combustion pipe 106 as a unit without a mechanical coupling to the combustion pipe 106. The cover plate 604, the fuel assembly 606, the support structure 602 and the perforated flame holder 400 can be configured to be retrofitted to the boiler 200 (see FIG. 21). The cover plate 604, the fuel assembly 606, the support structure 602 and the perforated flame holder 300 can be configured to be installed in and uninstalled from the boiler 200 as a unit for purposes of changing the porous flame holder 202. The cover plate 604 can be coupled to the exterior wall 103 of the shell 102 using threaded fasteners 608, for example.

In the prior art, a fuel assembly 606 may include swirl vanes 610 or equivalent structures (such as a bluff body, for example) aligned to cause vortices to form near to the fuel assembly 606, in cases where fluid fuel or composite fuel is used, as opposed to using solid fuel. The vortices operate to recycle heat released by a conventional flame back to incoming fuel and oxidant 206, 208 (see FIG. 21) to cause the flame to be maintained near the fuel assembly 606.

The illustrated support structure 602 can be configured to hold the perforated flame holder 300 away from the fuel nozzle 110 at a distance sufficient to cause substantially complete mixing of the fuel and oxidant at a location where the fuel and oxidant impinge upon the perforated flame holder 300; in other embodiments, the perforated flame holder may be closer or may include additional parts, such as electrodes for example, that are disposed closer or farther. Thermal insulation 612 can be included and operatively coupled to the flame holder support structure 602. The thermal insulation 612 can be supported by the support structure 602 adjacent to the wall of the combustion pipe 106 along at least a portion of the distance (D_(D)) between the fuel nozzle 110 and the perforated flame holder 300. In some embodiments, the thermal insulation 612 can be affixed to the combustion pipe 106 wall. Additionally or alternatively, thermal insulation 612 can be disposed adjacent to the wall of the combustion pipe 106 along at least a portion of the distance (D_(D)) between the fuel nozzle 110 and the perforated flame holder 400. For example, the thermal insulation 612 can be formed from a 1 inch thick FIBERFRAX DURABLANKET © high temperature insulating blanket, available from UNIFRAX I LLC of Niagara Falls, N.Y.

As mentioned above, in some cases the flame holder support structure 602 and the perforated flame holder 300 may be retrofitted to a boiler which already has associated with it a cover plate 604, held to the exterior wall 103 (usually by threaded fasteners 608) and a fuel assembly 606 held onto the cover plate 604. In such a case, the support structure 602 may be attached by various methods, such as welding the support structure 602 to the inside surface of the cover plate 604 (not illustrated), or drilling holes in the cover plate 604 and bolting the support structure 602 to the cover plate 604 with additional threaded fasteners 608 (such extra holes and fasteners are not shown in the drawing). The distal end of the support structure (the end farthest into the combustion pipe 106) may be mechanically supported and located by such an attachment. However, the inventors also contemplate that the support structure proximal end may be operatively coupled to at least one of the shell 102 (here, exterior wall 103) and the combustion pipe 106, as well as the cover plate 604. The distal end of the support structure 602, closer to the perforated flame holder 400, may be suspended in the space inside the combustion pipe 106, either coaxially or not coaxially, and with any amount of annular space between the support structure 602 and the inside of the combustion pipe 106. If the clearance space is minimal, then the inside of the combustion pipe 106 may support or help to support the support structure 602 against gravity (if the boiler is horizontal or slanted; if the boiler is vertical, then such support may not be needed).

In any case, the support structure should be positively located, so that it will not migrate due to vibration, for example.

Ideally, an existing boiler should be retrofitted with the least downtime and without requiring machine work. One embodiment of the support structure 602, which requires no machining or modification, no special tools, and no modification of existing parts for retrofitting with the perforated flame holder 400, includes a flange 614. This flange, which is unitary with or attached to the support structure 602, extends into the space between the outside surface of the exterior wall 103 of the shell 102, and the inward-facing surface of the cover plate 604. The flange 614 may replace, or augment, a gasket (not shown) which ordinarily or might otherwise be provided in that space for sealing purposes. The flange 614 not only seals, but also functions for mechanical support, and so may be made of strong metal such as steel; it may include a circular ridge or bead, like the beads in some internal combustion engine head gaskets, which may allow for sealing between the outside surface of the exterior wall 103 and the inward-facing surface of the cover plate 604. The flange 614 might also include, in this region, rings of elastomer or other soft gasket material, and/or grooves to accept such. The flange 614 may extend past the threaded fasteners 608 as shown, and include holes to pass the fasteners 608 through. These holes may provide one means for locating the support structure 602 relative to the combustion device.

The flange 614 may be considered as including three areas: an outer annular portion that is clamped tightly between the cover plate 604 and the exterior wall 103, by the threaded fasteners 608; an inner annular portion that is fastened to the support structure 602; and an intermediate annular portion that is neither fastened nor clamped. The outer annular portion is securely held, and the inner annular portion is fixed to a rigid body, namely the support structure 602.

If the combustion tube 106 is vertical, then there is no torque on the support structure 602, and the flange 614 may not need to resist any forces; but if the combustion tube 106 is tilted or horizontal, then there may be torque due to gravity at the proximal end of the support structure 602, and the flange 614 may need to resist it.

If the intermediate annular portion is narrow, then the flange 614 may be able to hold the support structure 602 against tilting. This is because the flange 614, in order to exert a torque on the support structure 602, needs only to resist bending, stretching, or failure due to shear force.

At the lower side of the flange 614, the gravity force may push the support structure 602 against the inside of the cover plate 604, so that the flange 614 needs to exert little force. However, at the upper side, the gravity force may tend to pull the support structure 602 away from the inside of the cover plate 604, and the flange 614 must resist this force.

It is evident that the intermediate portion may be subjected to only a shearing force if the intermediate portion is very narrow, but also to stretching and bending forces if the intermediate portion is broad. Assuming that the flange 614 is strong enough to resist plastic deformation or failure due to any of these forces, the movement of the support structure 602 may be least when there is only one: namely, shear, which predominates when the intermediate portion is narrow. Furthermore, if the intermediate portion is wide, and is able to assume an angle between the inner edge of the exterior wall 103 and the outer edge of the proximal end of the support structure 602, then the amount of tensile stretching of the intermediate portion may be minimal at the beginning of the displacement of the support structure away from the cover plate. This is because of the trigonometric fact that the cosine of a small angle is approximately one; at small angles, the amount of stretching is minimal, and therefore the flange 614 does not resist the motion of the support structure away from the cover plate. Thus, the support structure may tilt more under the force of gravity as the intermediate portion grows wider.

Therefore, to make the support structure 602 as stable as possible without requiring any modification of the other parts, the gap between the support structure and the inside of the exterior wall 103 should be minimized. Thus, one aspect of reaching the inventors' goal is to make the proximal end of the support structure 602 to fit as closely as possible inside the exterior wall 103 and/or the cover plate. The width of the intermediate portion is therefore less than a predetermined thickness, where the predetermined number depends of the thickness, shear modulus, tensile modulus, the weight of the support structure, the position of the center of gravity of the support structure, and other factors, which will be apparent to those skilled in the art. The predetermined thickness may be less than n inches, where n is a positive integer; or may be less than 1/n inches, where n is again an integer; or may be less than m/n inches, where m is an integer <n.

In most cases, the thickness of the flange 614 may not be a critical design issue, because the thickness can, in most cases, be increased to the point where support is not a design problem. For example, if the tolerance on the proximal opening into the combustion volume 108 is wide, or if several different openings are to be accommodated with one flange 614, then the thickness can merely be increased as needed.

The great advantage of the flange 614 is that it may require no modification of the other parts when installing a support structure 602. In particular, the existing cover plate 604 may require no modification.

It is to be noted that the illustrated support structure has application to combustion devices that lack a combustion pipe; one example would be a water-tube boiler, which lacks any well-defined surface surrounding the combustion volume 108. However, in cases where the applicants' concept is to be applied to combustion devices that include the exemplary illustrated combustion pipe 106, then a mechanical coupling to such a combustion pipe may be provided.

FIG. 24 shows a spring 670 fitted to the end of the support structure 602, according to an embodiment. Such a spring 670 may be provided to support the distal end of the support structure 602 if, for any reason, the flange 614 (see FIG. 23) is not to provide full support against its weight, or, if the flange 614 is to be omitted from the support structure 602. One or more such springs 670 can be fastened near the distal end of the support structure 602, either to help support the distal weight of the support structure 602, or to center the support structure 602, or both.

The spring 670 is fixed by a screw 671, but any permanent or temporary attachment can be used. As shown, the spring 670 is fixed near to the distal end of the support structure 602 but projects backward toward the proximal end, which may reduce the maximum temperature to which the spring 670 is exposed. If the combustion pipe 106 is metal in contact with water, then it may cool the spring 670. The spring 670 includes an up-turned proximal end so as to avoid catching when the support structure might be withdrawn.

As can be seen in FIG. 24, the spring 670 may extend only a short distance from the side of the support structure 602 when pressed onto it by a force. This may allow the support structure 602 to be inserted through a smaller opening.

FIG. 25 shows a variation on the spring 670, a spring 672 combined with a wheel carriage 674 that supports a wheel 676, according to an embodiment. As compared to the spring 670, the use of the wheel 676 reduces friction force applied against the inside surface of the combustion pipe 106, which may avoid wear or damage if the combustion pipe 106 is lined with, or made of, refractory material, rather than being made of metal as in the exemplary illustrated fire tube boiler 200 of FIG. 21.

Each wheel 676 may be made retractable into the body of the support structure 602 (not shown in FIG. 25), which may be done to allow the support structure to be inserted through a proximal opening of the least diameter (or opening width or distance if the space to be inserted into is not cylindrical), and provide the same advantage as mentioned above for the spring 670.

The drawing shows that the spring 672 is unitary with or fastened to the wheel carriage 674 that supports the wheel 676; these two may be combined into one integral piece of metal, by folding a sheet of metal, for example. At the end of the spring far from the wheel 676, the spring 672 is fastened to the support structure 602 (not shown in FIG. 25). On the other side of the wheel 676 an arm 678 attaches, which carries a weight 679. This weight 679 may be adjusted in size and/or placement to provide an outward or inward weight force on the wheel or wheels 676 jointly, such that the sum of the weight 679 forces counteracts gravity force on the support structure 602. It will be apparent that the screw 671, also seen in FIG. 24, together with the spring portion 672 of the folded-sheet-metal structure, can be considered as a fulcrum of a lever arm, by which the weight force of the mass 679 is amplified at the wheel 676. If the wheel 676 faces and bears downwardly as shown, then the leveraged force pushes against the inside of the combustion pipe 106 (not shown in FIG. 25); but if the wheel 676 is located above, on the opposite side of the support structure 602, then the bearing force of the wheel may be reduced. Furthermore, at intermediate points the force will be apportioned; for example, if the axis of the wheel is vertical, then the weight 679 exerts no leveraged force.

Thus, by properly deploying the wheels 676 and by properly biasing them with weights 679, the weight of the support structure 602 can be effectively canceled, so that the support structure 602 levitates and, as a consequence, automatically centers itself under the influence of the forces due solely to the springs 670, 672 (which, if these forces are equal and equally spaced, would center the support structure 602 inside the combustion pipe 106).

A cover (not shown) may be provided to keep flames away from the wheel 676 and reduce its operating temperature. The cover may also act as a structural reinforcement, if for example formed as a stiffening rib of bent sheet metal or metal plate.

FIG. 26 depicts a variable-distance arrangement, according to an embodiment. As mentioned above, the dilution distance D_(D) extends from the perforated flame holder 400 to the fuel nozzle 110. It may be desirable to vary this distance. Therefore, the support structure may have a more-distal cylindrical portion in which the perforated flame holder 400 can slide (or, a prismatic portion if the perforated flame holder 400 has a non-circular outline, and is to fit snugly and/or slide inside the combustion pipe). Alternatively, the support structure 602 may include a base portion and a sliding portion, where the perforated flame holder 400 is fixed to the sliding portion and the sliding portion slides on an outside of the base portion, in the manner of an engine cylinder sliding on a piston. However, these portions may be either cylindrical, as are pistons and cylinders, or prismatic (regardless of whether the perforated flame holder 400 is round or not round).

FIG. 27 shows a support structure 602 (see FIGS. 23, 24, and 26) that is adapted for changing the dilution distance D_(D) from outside of the assembled boiler, without requiring any modification of the cover plate 604 (see FIG. 23), or other “package boiler” parts. This embodiment embeds a gear train in the flange 614 (see FIGS. 23 and 26), and uses a single-ply or multi-ply metal sandwich in place of single-ply metal. Single-ply and multi-ply sheet-metal gaskets have long been used as IC engine head gaskets; the multiple sheet-metal plies are spot-welded together to form a unitary gasket, and/or glued together with neoprene or the like. The same type of construction can be used here, and the flange 614 may be a multi-ply composite. A gear in the gear train may have an axial pin, which is held in a hole in an adjacent sheet-metal ply on at least one side.

There may be three gear trains (or a different number) embedded in the flange 614, and each gear train may rotate the proximal end of a respective rod 620. Each of the exemplary three rods 620 is rotatable by being fastened to or unitary with a respective rod-end gear 622, that is trapped within a respective end-gear cavity 616 formed by: a hole or molded depression in the flange 614; the inside surface of the cover plate 604; and/or a proximal surface of a part of the support structure 602 lying beyond the distal surface of the flange 614.

Each rod-end gear 622 is engaged with at least one drive gear 624 in a respective gear train, that drives the rod-end gear 622. The one or more drive gears 624 are engaged with one another successively as needed to the point where one of them extends beyond the outer edge of the cover plate 604. At that point, the gear train can be driven by a motor gear 626 meshing with the outermost drive gear 624. In some cases not shown, due to the geometry of the exterior wall 103 and the cover plate 604, no drive gears may be needed, as the rod-end gear 622 will protrude from under the edge of the cover plate 604.

The three rods 620, being simultaneously turned by their respective gear trains, can cause the perforated flame holder 400 to move in the axial direction (along the dot-dash line in FIG. 23) to vary the dilution distance D_(D) if the rods 620 are each similarly threaded and engage female threads 618 (see FIG. 26) of the perforated flame holder 400, a peripheral frame 406 (see FIG. 26) of the perforated flame holder 400, or a sliding portion of the support structure 602, mentioned above.

FIG. 27 shows one particular embodiment of the flange 614. This embodiment uses a sandwich of three sheets of metal 6141, 6142, and 6143, with the outer two sheets 6141 and 6143 being flat; this has the advantage of providing a flat-surfaced flange 614, which may be sealed with conventional sealing techniques used when the flange 614 is not present (e.g., in the original “package” unit, which might use a non-metallic gasket, not shown, between the cover plate 604 and the exterior wall 103). The middle sheet 6142 is punched or machined to create spaces for the drive gears 624 and the rod-end gears 622. The outer two sheets 6141 and 6143 are drilled, punched, or the like to provide bearing holes for axial pins 6145 of the drive gears 624, which, being supported on two sides rather than one, can resist skewing forces and work more reliably.

In the region of the intermediate annular portion, which, as discussed above, helps to resist torque when the support structure 602 is horizontal, the three sheets 6141, 6142, and 6143 may be rigidly fastened together by spot-welding, strong adhesives, and/or fasteners, or the like. Most preferably for resisting torque, the rods 620 can be arranged so that, when viewed axially, the uppermost region of the intermediate portion of the flange 614 (which is the region subjected to the most mechanical stress) is far from the rods 620. For example, one rod may be in the lowermost region and two others disposed at 120 degrees either side. It will be understood that the middle sheet 6142 may be present everywhere except where gears are present, so that the stiffness of the basket 614 is maximized.

In the rest of the flange 614, the mechanical strength requirements are lower, but sealing is a desirable option. Ideally, the flange 614 might not allow combustion products to exit the combustion volume 108, or outside air to leak in. To this end, any gaps between the sheets 6141, 6142, and 6143 may be filled with sealant. Another option is a stuffing box 6144 through which the rod 620 passes.

On the outside, for each of the several gear trains and rods 620, there may be provided a drive motor incorporating a motor gear 626 meshing with the outermost drive gear 624. The drive motor may include feet (not shown) with holes positioned so that one or more of the threaded fastener 608 may serve to locate the drive motor. Then, the drive motors for the several rods 620 may be simultaneously controlled to move in synchrony so that the perforated flame holder 400 may move along the direction of the dot-dash line in FIG. 23 without becoming skewed.

An advantage of the embodiment shown in FIG. 26 and FIG. 27 is that an adjustable dilution distance D_(D) is provided, but no modifications are needed if the cover plate 604 is a pre-existing or given part of the device. The inventors also contemplate a cover plate 604 with holes already drilled for passage of the rods 620 to the outside, which would avoid the complication of gears; but, if there is already a cover plate 604 without such holes, as in a “package boiler” for example, then the embodiment provides for an adjustable dilution distance D_(D) without any modifications being needed; only disassembly of the parts other than the support structure 602, and reassembly with the support structure 602, are needed. A flange with gears may not be unduly expensive, nor require difficult maintenance (the gears can be oiled from the outside with just an oil can), nor be difficult or expensive to fix.

A large load on the gears is only likely to result if the distal threaded portion of the rod 620 freezes onto the female threads 618 due to corrosion, buildup of combustion products, etc. Such problems can be prevented by moving the perforated flame holder 400 through a short distance at regular intervals, and this can be programmed into whatever device controls the drive motors.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

What is claimed is:
 1. A furnace, comprising: a fuel and oxidant source configured to output fuel and oxidant, a perforated flame holder configured to hold a combustion reaction supported by the fuel and oxidant source; and a support structure configured to hold the perforated flame holder in alignment with the fuel and oxidant output by the fuel and oxidant source; wherein the support structure comprises a mechanical coupling between the perforated flame holder and an attachment point of the furnace.
 2. The furnace of claim 1, wherein the mechanical coupling comprises a cooling fluid channel configured to convey cooling fluid to at least a portion of the support structure, an actuator configured to cause a position change of at least a portion of the support structure, or a cooled actuator configured to cause a position change of at least a portion of the support structure.
 3. The furnace of claim 1, wherein the perforated flame holder is configured by thermal and structural reaction parameters thereof to contain a flame therein at the location, when the fuel and oxidant has a predetermined mix ratio and a predetermined velocity, and the fuel has a predetermined heat value.
 4. The furnace of claim 1, wherein the perforated flame holder has a substantially uniform thickness between a first flame holder surface and a second flame holder surface.
 5. The furnace of claim 1, wherein the support structure further comprises a strut extending from an interior surface of the furnace to the perforated flame holder through an intervening space.
 6. The furnace of claim 5, wherein the strut is canted in a direction opposite to a velocity of the fuel and oxidant from the fuel and oxidant source.
 7. The furnace of claim 1, wherein the support structure further comprises a fastener attached to a wall of the furnace.
 8. The furnace of claim 7, wherein the fastener further comprises a weld.
 9. The furnace of claim 7, wherein the fastener further comprises a bolt or stud.
 10. The furnace of claim 2, wherein the support structure further comprises a tension member.
 11. The furnace of claim 2, wherein the support structure further comprises a compression member.
 12. The furnace of claim 1, wherein the support structure further comprises a rail.
 13. The furnace of claim 2, wherein the attachment point of the furnace further comprises at least one furnace tube with which the support structure is mechanically coupled.
 14. The furnace of claim 13, wherein the furnace further comprises a fire-tube boiler and the furnace tube further comprises the attachment point.
 15. The furnace of claim 2, wherein the support structure is attachable to and detachable from the furnace at the attachment point.
 16. The furnace of claim 1, wherein the furnace further comprises a burner tile, and the support structure is configured to couple to the burner tile.
 17. The furnace of claim 1, wherein an interior surface of the furnace further comprises an area that faces into, or is adjacent to an opening into or out of, an interior space of the furnace, and wherein the support structure engages with a plate to which the fuel and oxidant source is mounted, and the plate is configured to the opening.
 18. The furnace of claim 1, wherein the support structure further comprises a coolant space therein, the coolant space being bounded by a fluid-containment barrier; the coolant space being separated from combustion by the fluid-containment barrier.
 19. The furnace of claim 18, further comprising coolant disposed in the coolant space.
 20. The furnace of claim 18, wherein the support structure is metallic and the perforated flame holder is non-metallic.
 21. The furnace of claim 18, wherein the fluid-containment barrier further comprises a fluid connection between the coolant space and a space outside of the perforated flame holder.
 22. The furnace of claim 21, wherein the fluid connection further comprises a coolant conduit passing through a wall of the furnace.
 23. The furnace of claim 22, wherein the support structure further comprises the coolant conduit.
 24. The furnace of claim 22, wherein an attachment point of the furnace comprises the coolant conduit.
 25. The furnace of claim 24, wherein the coolant conduit further comprises a hollow bolt passing through the wall of the furnace.
 26. The furnace of claim 21, further comprising a heat radiator located in the space outside of the perforated flame holder and a space outside of the furnace, and wherein the radiator is fluid-coupled to the coolant space by the fluid connection.
 27. A method of removing heat from a furnace, the furnace comprising: a fuel and oxidant source configured to output fuel and oxidant, a perforated flame holder configured to hold a combustion reaction supported by the fuel and oxidant source; and a support structure configured to hold the perforated flame holder in alignment with the fuel and oxidant output by the fuel and oxidant source, the support structure further comprising a coolant space therein, the coolant space being bounded by a fluid-containment barrier and separated from combustion by the fluid-containment barrier; the method comprising: supporting the perforated flame holder to receive a flow of fuel and oxidant with a flame holder support structure; holding a combustion reaction supported by the fuel and oxidant with the perforated flame holder; and cooling the perforated flame holder support structure by placing the flame holder support structure in contact with a fluid coolant having a coolant temperature lower than a combustion temperature.
 28. The method of removing heat from the perforated flame holder of claim 27, further comprising moving the fluid coolant relative to the perforated flame holder support structure.
 29. The method of removing heat from the perforated flame holder of claim 27, wherein the fluid coolant includes air.
 30. The method of removing heat from the perforated flame holder of claim 27, wherein the fluid coolant includes a liquid.
 31. The method of removing heat from the perforated flame holder of claim 30, further comprising boiling the liquid within the coolant space.
 32. The method of removing heat from the perforated flame holder of claim 27, wherein the fluid coolant includes sodium.
 33. The method of removing heat from the perforated flame holder of claim 27, further comprising moving the coolant to a heat radiator outside of the furnace.
 34. The furnace of claim 1, wherein the support structure further comprises a mechanism configured to move the perforated flame holder relative to the furnace and/or the fuel and oxidant source.
 35. The furnace of claim 34, wherein the mechanism is configured to move the perforated flame holder into and/or out of a cooling region wherein the perforated flame holder and/or the support structure is cooled.
 36. The furnace of claim 35, wherein the mechanism moves the perforated flame holder continually or continuously over a path that passes through a fuel and oxidant-impingement region and the cooling region.
 37. The furnace of claim 34, wherein the support structure further comprises a rail, and the perforated flame holder is mounted on the rail by a slider mechanism.
 38. The furnace of claim 34, wherein the perforated flame holder revolves or rotates.
 39. The furnace of claim 38, wherein the perforated flame holder further comprises a belt of hinged links.
 40. The furnace of claim 34, wherein the mechanism is configured to vary a distance between the perforated flame holder and the fuel and oxidant source by moving the perforated flame holder, relative to the furnace, in a direction that is parallel to a flow of fuel and oxidant and/or transverse to a first flame holder surface.
 41. The furnace of claim 40, wherein the fuel and oxidant source is non-movable relative to the furnace.
 42. The furnace of claim 34, wherein the mechanism moves the perforated flame holder, and further comprising an additional mechanism that moves the fuel and oxidant source relative to the furnace.
 43. The furnace of claim 34, wherein the support structure is mounted on a burner tile, and the mechanism moves the perforated flame holder relative to the burner tile.
 44. The furnace of claim 34, wherein the mechanism puts the support structure into sliding or rolling contact with an interior surface of the furnace.
 45. The furnace of claim 44, wherein the contact is made at least partially by a wheel comprised in the mechanism.
 46. The furnace of claim 44, wherein the mechanism further comprises a rail mounted on the interior surface of the furnace and the support structure slides or rolls on the rail.
 47. The furnace of claim 46, wherein the rail is substantially parallel to an axis of a cylindrical or prismatic portion of the interior surface.
 48. The furnace of claim 34, wherein at least one of the support structure or the mechanism further comprises a compression member in contact with an attachment point of the furnace.
 49. The furnace of claim 34, wherein at least one of the support structure or the mechanism further comprises a tension member in contact with an attachment point of the furnace.
 50. The furnace of claim 34, wherein the mechanism rotates the perforated flame holder within the furnace.
 51. The furnace of claim 50, wherein the perforated flame holder is rotated about an axis that that is not parallel to a direction of flow of fuel and oxidant.
 52. The furnace of claim 34, wherein the support structure engages with a mounting plate to which the fuel and oxidant source is mounted, and the support structure further comprises the mechanism.
 53. The furnace of claim 52, wherein the support structure further comprises a flange disposed between the plate and the interior surface.
 54. The furnace of claim 34, wherein the mechanism further comprises an actuator.
 55. The furnace of claim 54, wherein the actuator further comprises a motor.
 56. The furnace of claim 34, wherein the mechanism further comprises a screw and/or a gear.
 57. The furnace of claim 34, wherein the mechanism further comprises a feedback loop further comprising a processor and a sensor; wherein the perforated flame holder is configured by thermal and structural reaction parameters thereof to contain a flame therein when located at a distance from the fuel and oxidant source at which the flow has a predetermined velocity and a predetermined mix ratio, and the fuel has a predetermined heat value; and wherein the feedback loop varies the distance under control of the processor to maintain the flame within the perforated flame holder.
 58. A method of reducing combustion emissions emitted by a furnace, the furnace comprising: configuring a perforated flame holder by thermal and structural reaction parameters thereof to contain a flame therein at a position, when a fuel-oxidant mixture from the fuel and oxidant source has a predetermined mix ratio and a predetermined velocity, and the fuel has a predetermined heat value; providing an electronic feedback device operatively coupled to a flame sensor and the mechanism; and moving the perforated flame holder, under control of the feedback device reacting to signals from the flame sensor, to contain the flame inside the perforated flame holder and/or to reduce emissions.
 59. The method of reducing combustion emissions of claim 58, wherein the electronic feedback device further comprises a processor running software embodied in a non-transitory medium.
 60. The method of removing heat from the perforated flame holder of claim 58, comprising: using the mechanism to move at least a portion of the perforated flame holder between a flame and a cooling region. 